1. Field of the Invention
The present invention is related to a stream transmission apparatus, method, and transmission and reception system; and more particularly, a stream transmission apparatus, method, and transmission and reception system of DRM content with reverse traceability.
2. Discussion of the Related Art
A video streaming service can be divided largely into a stage of preparing target content to be streamed and a service stage of streaming the content upon request of a user or a terminal. Service providers apply a Digital Right Management (DRM) technology to prevent leakage and duplication of content by third parties. A DRM encryption technology is applied while content is still in a compression state through one of a plurality of video compression encoders. In other words, first of all, content is compressed in a content preparation stage and undergoes an encryption process. Afterwards, the encrypted content is transmitted in the form of a file at the service stage.
However, the DRM technology is inadequate to block the leakage and duplication of decrypted content. In this regard, a forensic watermarking technology is needed, which is capable of reversely tracking a leakage path of the corresponding content. Forensic watermarking inserts forensic marks into target content by modifying RGB values of the content and saving the modified RGB values while the target content is in a decompressed state. Therefore, DRM encryption is possible only when forensic watermarks are inserted into target content before it is compressed.
To insert forensic watermarks, however, user- or User Equipment (UE)-specific information needs to be incorporated; therefore, the forensic watermarks are inserted after user-specific information is obtained. In this reason, conventional systems provide streaming services by decrypting encrypted content, decompressing the decrypted content, inserting forensic watermarks, re-compressing the content, and performing re-encryption of the content. The process consisting of decrypting, decompression, re-compression, and re-encryption can be regarded highly inefficient in terms of time and costs. Also, the conventional technology is incapable of transmitting HD content and can play only a limited number of streams even with high performance hardware.